Fe-monticellite in serpentinites from the Happo ultramafic complex
Fe-monticellite in serpentinites from the Happo ultramafic complex
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来自 Happo 超镁铁杂岩的蛇纹岩中的铁蒙锂石
DOI：
10.1016/j.lithos.2020.105686
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发表时间：
2020
期刊：
影响因子：
3.5
通讯作者：
Nozaka Toshio
中科院分区：
文献类型：
--
作者：
Tsuji Tetsuro;Doi Kentaro;Kawano Satoyuki;Nozaka Toshio
在日本中部Happo超镁铁质杂岩的蛇纹状橄榄岩中新发现的Fe单陨石表明，它取代了橄榄石，并与反辉石共生。单颗陨石以几种形式存在：作为离散的颗粒；部分不相连的环或圆形带状；边缘地幔或切割橄榄石的脉状；或作为小的赤道颗粒的聚集体。它显示出与强烈剪切的反辉石基质的质地对比。与反辉石和透辉石共存，单陨石富铁组分表明其形成温度为300-350℃，这一极低的单陨石形成温度与观察到的结构相一致，表明其在Happo杂岩高温(400-600℃)蛇纹岩作用期间，在糜棱岩化之后的蛇纹岩化阶段静态形成。二长花岗岩中含有细小的芒硝石包裹体，表明它是在还原条件下形成的，这是橄榄石蛇纹石化的特征。二长花岗岩比残馀橄榄石富铁、富锰，与共存的反钙辉石中这些元素的缺乏程度相适应。没有证据表明钙的添加来自外部来源。然而，在透闪石被蛇纹石取代的地方，透辉石生长在残留橄榄石的反面，部分被单陨石取代。因此，透闪石可能是形成单陨石的钙源。这些结构关系和共生的热力学计算表明，二辉石是由橄榄石和水流体反应形成的，这些流体携带透闪石释放的钙，在蛇纹岩作用过程中受二氧化硅化学势的局部梯度驱动。
The new discovery of Fe-monticellite in serpentinized peridotites of the Happo ultramafic complex, central Japan, shows it replacing olivine and coexisting with antigorite. The monticellite occurs in several forms: as discrete grains; partially disconnected rings or circular ribbons; fringing mantles or in veins cutting olivine; or as aggregates of small equant grains. It shows a textural contrast to the intensely sheared matrix of antigorite. The coexistence with antigorite and diopside, and the Fe-rich compositions of monticellite indicates that it formed at 300–350 °C. This extremely low-temperature for monticellite formation is consistent with the observed textures indicative of its static formation at a stage of serpentinization that followed mylonitization during high-temperature (400–600 °C) serpentinization in the Happo complex. The monticellite contains minute inclusions of awaruite, which indicates formation under reducing conditions, as is characteristic of serpentinization of olivine. The monticellite is richer in Fe and Mn than relict olivine, being commensurate with deficiencies of these elements in coexisting antigorite. There is no evidence of Ca addition from an external source. However, where tremolite is replaced by serpentine, diopside grows at the opposite side of relict olivine that is partly replaced by monticellite. Thus, tremolite is the likely source of Ca for monticellite formation. These textural relationships and the thermodynamic calculations for paragenesis indicate that monticellite formed by reactions between olivine and aqueous fluids, carrying Ca released from tremolite, that were driven by a local gradient of SiO2chemical potential during serpentinization.
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影响因子：
3.5
作者：
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通讯作者：
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影响因子：
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作者：
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DOI：
--
发表时间：
1978
期刊：
--
影响因子：
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作者：
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通讯作者：
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影响因子：
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作者：
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通讯作者：
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